This invention relates generally to a printed circuit board connector and, more particularly, to a zero insertion force printed circuit board connector having cam means therein for actuating the contacts into engagement with the pads along the edge of a printed circuit board.
It is well known in the art that substantial force is required to insert a printed circuit board into a connector having a large number of spring contacts therein due to the resilient engaging force of the contacts with the edge of the board. As the number of contacts is increased in a connector, the amount of force required to insert the printed circuit board into the connector, or to withdraw it from the connector, may become excessive for practical use. In addition, the direct insertion of boards into connectors having spring contacts therein results in a wiping action occurring between the contacts and the pads on the edge of the board, which causes excessive wear of the pads over lengthy periods of use of the connector. It is therefore a common practice in the art to provide a zero insertion force printed circuit board connector in which the contacts are mounted so that they are out of the path of movement of the board when it is inserted into the connector whereby no resistance is encountered upon inserting the board thereinto. Thereafter the contacta are cam actuated into engagement with the pads on the edge of the board. When it is desired to remove the board from the connector, the cam actuation mechanism is released, so that the contacts are no longer frictionally engaging the pads on the board, thus allowing the board to be freely removed from the connector. U.S. Pat. No. 3,526,869 discloses a zero force printed circuit board connector in which a rotatable cam pushes a longitudinally movable slide cam element that cams the contacts into engagement with the pads on a printed circuit board inserted into the connector. U.S. Pat. No. 3,478,301 discloses a zero force printed circuit board connector in which the board actuates cam blocks in the connector which in turn cam the contacts into engagement with the board when the board is inserted into the connector. It is also known in the art to provide a zero force printed circuit board connector in which a movable cam on the connector housing acts directly upon the contacts to actuate them. Examples of these connectors are found in the following U.S. Pat. Nos. 3,475,717; 3,329,926; and 3,568,134. U.S. Pat. No. 2,857,577 discloses a zero force connector in which a housing is frictionally mounted downwardly over contacts secured in a substrate. Sliding downward motion of the housing cams the contacts into engagement with the printed circuit board inserted in the housing. IBM Technical Disclosure Bulletin entitled, "Low Voltage Pluggable Connector", by C. B. Hill et al., Vol. 8, No. 12, May 1966, discloses a zero force connector similar to that disclosed in the aforementioned Pat. No. 2,857,577 in which the housing is moved over the contacts to cam them by means of screws which extend upwardly through the substrate and are threadedly received in holes in the bottom of the housing. Such an arrangement requires at least four screws, one at each corner of the connector housing, to assure that the housing is firmly and uniformly seated on the substrate so that a uniform camming force is applied to the contacts urging them into engagement with the pads on a printed circuit board mounted in the housing. The use of a number of screws to mount the housing over the contacts is obviously time consuming. Moreover, it is frequently very inconvenient, if not impossible, to actuate screws from the bottom of a mounting substrate for a connector housing in an electronic packaging assembly.
It is the purpose of the present invention to provide a zero force printed circuit board connector of the general type disclosed in the aforementioned IBM bulletin with a cam actuating mechanism which moves the housing in a uniform, controlled manner over the contacts to simultaneously and uniformly cam the contacts into engagement with a printed circuit board mounted within the connector housing. It is also a purpose of the invention to provide such a connector in which the cam actuating mechanism is mounted in a position where it is easily accessible for operation by the user, and allows actuation of the housing with only a single simple motion, thus overcoming the disadvantages of the aforementioned IBM connector.